In one aspect, a winglet for a rotor blade is disclosed. The winglet may generally include a winglet body extending at least partially between a winglet origin and a blade tip. The winglet body may define a sweep and a pre-bend. The sweep defined between the winglet origin and the blade tip may range from about 0.5% to about 4.0% of a span of the rotor blade. The pre-bend defined between the winglet origin and the blade tip may range from about 1.5% to about 4.5% of the span of the rotor blade.